United States Department of Transportation
i
Safety Evaluation of Multiple Strategies at Signalized Intersections
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2018-05-01
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[PDF-3.07 MB]
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OCLC Number:1041193644
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Abstract:The Development of Crash Modification Factors program conducted safety evaluations of multiple strategies at signalized intersections for the Evaluation of Low Cost Safety Improvements Pooled Fund Study. This study evaluated multiple low-cost treatments at signalized intersections. Improvements included basic signing, pavement marking, and signal enhancements. This strategy was intended to reduce the frequency and severity of crashes at signalized intersections by alerting drivers to the presence, type, and configuration of the approaching intersection. Geometric, traffic, and crash data were obtained at three- and four-legged, two- and four-lane major road, urban, and rural signalized intersections in South Carolina. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before–after analysis was conducted using reference groups of untreated intersections with characteristics similar to the treated sites to develop safety performance functions for the intersection configurations included in this study. The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the treatments. The aggregate results indicate reductions for all crash types analyzed (i.e., total, fatal and injury, rear-end, right-angle, and nighttime). The crash modification factors (CMFs) for fatal and injury and right-angle crashes were 0.893 and 0.883, respectively, which were statistically significant at the 95‑percent confidence level. The CMFs for total, rear-end, and nighttime crashes were 0.955, 0.974, and 0.969, respectively, which were not statistically significant at the 95-percent confidence level. Note that the CMF for total crashes was statistically significant at the 90-percent confidence level. The benefit–cost ratio estimated with conservative cost and service life assumptions was 4.1:1 for total crashes at signalized intersections. The results suggest that the implementation of multiple low-cost treatments, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective.
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